Process of producing low-carbon metals or alloys.



No. 790.396. PATENTED MAY 23, 1905. E. P. PRICE.

PROCESS OF PRODUCING LOW CARBON METALS 0R ALLOYS.

APPLIDATIOK FILED NOV. 22. 1904.

Patented May 23, 1905.

PATENT OFFICE.

EDGAR F. PRICE, OF NIAGARA FALLS, NEIV YORK.

PROCESS OF PRODUCING LOW-CARBON METALS OR ALLOYS.

SPECIFICATION forming part of Letters Patent No. 790,396, dated May 23,1905.

Application filed November 22,1904. Serial No. 233.886.

T0 (1/7/7 7070mm it ntu/y concern:

Be it known that I, EDGAR F. PRICE, a citizen of the United States,residing at Niagara Falls, in the county of Niagara and State of NewYork, have invented certain new and useful Improvements in Processes ofProducing Low-Carbon Metals or Alloys, of which the following is aspecification.

In the production of ferrochromium from chromite it is customary tointroduce a small charge of the ore, carbon, and a flux into an electricfurnace having sides and a hearth of carbon and to spring an. arebetween the hearth and a depending carbon electrode having its lower endembedded in the charge. A high-potential difference is usuallymaintained between the terminals of the furnace. As the ore is reduced alayer of the fcrrochromium accumulates on the hearth covered by a layerof slag. The molten alloy is tapped out from time to time until the slaghas in creased to such an amount as to require removal. As the normalslag has a high. fusionpoint, a flux is added to render it more liquidand the remaining alloy and slag are finally run out through the metaltap-hole. The furnace is then charged anew and the process is repeated.

It is important that the ferrochromium produced should be low in carbon.The amount of carbon in the charge is therefore ordinarily kept at aminimum. On account of the low percentage of admixed carbon, however,highly-oxidizing gases are evolved in contact with the dependingelectrode, whichis soon consumed and must be replaced. The air also actsrapidly on the hot electrode when the furnace is emptied by the removalof slag. Since the charge is a fairly good conductor of electricity, athin layer only is maintained around the lower end of the dependingelectrode to prevent excessive shunting of current to the carbon sidesof the furnace under the high applied potential. Much heat is thereforelost by radiation from the zone of reduction through the charge, Whilethe electrode is insufficiently protected from oxidation by the air.This loss of heat greatly decreases the reduction efficiency of thefurnace. Furthermore, the slag is not kept at a sufficiently hightemperature to permit it to be tapped out, except by adding largeamounts of flux, discontinuing the charging of ore, and employing theenergy of the are merely to liquefy the slag. The heat losses are alsoincreased by the discontinuous mode of working both the furnace and thedepending electrode cooling down when the furnace is emptied. It is'alsoimpracticable to eflect a clean separation of the metal and slag byremoving them successively through a single tap-hole.

According to the present invention the production of low-carbonferrochromium and other metals and alloys is effected by a continuousoperation comprising two stages. In the first stage an alloy with arelatively high percentage of carbon is produced by smelting a chargecontaining suflicient carbon to protect the carbon electrodes. loy isthen run into a second furnace or into another compartment in the samefurnace and is subjected to the action of a decarburizing agent. Thepreferred reagent is lime, and a layer of molten lime is preferablymaintained on the surface of the molten alloy until the desiredpercentage of carbon has been withdrawn, the carbon reacting on the limeto produce calcium carbid which is separated l'rom the purified alloy.

Suitable apparatus for carrying out the process is shown in theaccompanying drawings, in which- Figure 1. is a transverse verticalsection of separate electric furnaces for reducing the ore anddecarburizing the alloy, and Fig. 2 is a transverse vertical section ofan electric furnace having separate communicating compartments foreffecting the reduction and decarburization.

The reduction-furnace shown in Fig. 1 comprises sides 1, of refractorynon-conducting material, such as chromite or magnesia, and a hearth 2,of carbon, surrounded by a metal casing 3, having an electric terminal3. The carbon hearth constitutes one electrode. The other electrode is adepending carbon rod 4. Tap-holes 5 6 extend through the side walls atdifferent heights. In using this furnace to carry out the first stage ofthe The molten alprocess an arcis established between the dependingelectrode and the carbon hearth, and a small amountof the chargeforexample, a mixture of chromite, @ie, li nle, and silica-4s fed into thefurnace. The charge preferably contains a considerable excess of carbonto protect the electrode 4 from oxidation. The furnace is then graduallyfilled until in its normal working condition the depending electrode isembedded in the charge. As the ore is reduced superposed layers of slagand ferrochromium collect in the bottom of the furnace and are withdrawnfrom time to time through the tap-holes 5 6, thealloy being run into thedecarburizing-furnace 7. More of the charge mixture is then fedinto thereduction-furnace. The furnace 7 comprises a body 8, of refractorymaterial,

referably chromite or magnesia, surrounded by a metal casing 9.superposed tap-holes 10 11 extend from the lower part of the furnace.Carbon-rod electrodes 12 13 of opposite polarity depend into thefurnace. In the second stage of the process after a layer of thehigh-carbon alloy has been run into the furnace 7 a body 14 of the limeor other decarburizing agent is fed into the furnace upon the alloy anda portion of the lime is melted by an electric current and maintained asa molten layer 15 upon the alloy. The carbon of the alloy istherebygradually withdrawn, reacting on the lime to produce calcium carbid. Asdecarburization progresses the calcium carbid is withdrawn at intervalsthrough the tap-hole 10 and the purified alloy through the tap-hole 11.More of the highcarbon alloy is then supplied from thereduction-furnace, percolating through the lime to the bottom of thefurnace, and the body of lime is replenished as required. In case it isnot desired to entirelydecarburize the product portions of thehigh-carbon alloy may be run 1nto the furnace 7from time to time and thebodyof metalallowed to accumulate, portions being withdrawn when thecarbon has been reduced to the desired percentage. By maintaining aconsiderable pool of metal in the furnace 7 portions of the high-carbonalloy may be frequently added and portions of the product withdrawnwithout materially changing the carbon contents.

The furnace 16 (shown in Fig. 2) has separate communicating compartments17 1.8 for reducing the ore and decarburizing the alloy. Thereduction-compartment 17 has non-conducting sides 20 and a hearth 21,ofcarbon, surrounded by a metal casing 22, having an electric terminal22. The carbon hearth constitutes one electrode. A tap-hole 23 for slagextends through the end wall. The decarburizing-compartment 18. has abottom 2 1 and outer walls 25, of non-conducting. material, preferablychromite or magnesia. .Superposed lateral tap .-holes 26 27 extendthrough the end Wall.- The. compartments 17 18 are artially separated bya transverse wall 28, w 'ch depends nearly to the bottom of the furnace.This wall preferably con- ,sists of a steel casting 29, having'a chamberfor the circulation of water and an outer facing 30 ofrefractorymaterial. A passage 31 beneath the wall 28 connects thecompartments 17 18. A carbon-rod electrode 32 of opposite polarity tothe terminal 22 depends .into thereduction-compartment. Two carbon-rodelectrodes 33 34 of opposite polarity depend into thedecarburizingcompartment. In using this furnaceto carry out the processthe charge of ore, carbon, and flux is smelted in the compartment 17 byan electric current passing between-the electrode 32 and the carbonhearth 21. The resultingslag is withdrawn from time to time through thetap-hole 23, and the high-carbon alloy runs through the passage .31 intothe compartment 18. -The decarburization of the alloy in thiscompartment is efl'ectedprecisely as in the separate furnace 7,heretofore described, a bodyof the decarburizing agent being supportedupon the alloy: and. heated by an electric current. The calcium carbidis withdrawn through thev tap-hole 26 and the purified alloy through thetap-hole 27. The process is carried out in a continuous manner, thecharge mixture being fed into the compartment 17 and lime into thecompartment 18, and the slag, carbon, and purified alloy being withdrawnthrough the tap-holes 23 26. 27 as required.

The process hasbeen described in connection with theproduction offerrochromium, but is applicable to the production of various low-carbonmetals and alloys. It enables a metal containing a minimumorpredetermined low percentage of carbon to be con- I tinuously producedat a relatively low cost. By employing a charge containing an excess ofcarbon and by embedding the depending electrode in a considerablebodyofthe charge the ordinary reduction-furnace may be em-, 'ployed andthe usual loss by oxidation of the carbon electrodes largely prevented.The carbonin the alloy is thenremov'ed or. re-

duced to the desired figure bya cheap reagent and in a furnacehaving-non-carbon walls, the heat in the high-carbon alloy beingretained by running it in a molten condition into thedecarburizing-furnace.

I claim 1. The process of roducing low-carbon metals or alloys, whichconsists in first producing a materialrelatively-high in carbon,removing the molten high-carbon product from the zone of reduction,treating it with a decarburizing agent and producing a nongaseouscarburized lay-product, and separating'the by-product from thelow-carbon product, as set forth.

2. The process of continuously producing low-carbon metals oralloys,whic consists IIO in first producing a material relatively high incarbon, running the molten high-carbon product into a separate chamber,treating it with a decarburizing agent and producing a nongaseouscarburized by-product, and separat ing the byproduct from the low-carbonproduct, as set forth.

3. The process of continuously roducing low-carbon metals or alloys,whic consists in first producing a material relatively high in carbon,running the molten hi gh-carbon product into a separate chamber,electrically heating it in the presence of a decarburizing agent andproducing a non -gaseous carburized byproduct, and separating theby-product from the low-carbon product, as set forth.

4. The process of continuously producing lowcarbon metals or alloys,which consists in first producing a material relatively high in carbonby electrically smelting a charge containing an excess of carbon,separating the resulting slag, running the molten high-carbon productinto a separate chamber, electrically heating it in the presence of adecarburizing agent and producing a nongaseous carburized by-product,and separating the by-product from the low-carbon product, as set forth.

5. The process of continuously producing low-carbon metals or alloys,which consists in first producing a material relatively high in carbonby electrically smelting a charge containing an excess ol carbon,separating the resulting slag, running the molten high-carbon productinto a separate chamber, electrically heating it in the presence of adecarburizing agent and producing a nongaseous carburized by-product,separating the byproduct from the low-carbon product, and supplying thecharge mixture and deearburizing agent and withdrawing the slag, by--product and low-carbon product as required, as set forth.

6. The process of continuously producing low-carbon metals or alloys,which consists in first producing a material relatively high in carbonby electrically smelting, with carbon electrodes, a charge containing anexcess of carbon, protecting the electrodes from oxidation by aconsiderable body of the charge, separating the resulting slag, runningthe high-carbon product into a separate chamber having non-carbon walls,treating it with a decarburizing agent and producing a non gaseouscarburized byproduct, separating the by-product from the low-carbonproduct, and supplying the charge mixture and dccarburizing agent andwithdrawing the slag, byproduct and low-carbon product as required, asset forth.

7. The process of continuously producing low-carbon metals or alloys,which consists in first producing a material relatively high in carbon,running the molten high-carbon product into a separate chamber andtreating it with lime, and separating the resulting calcium carbid fromthe low-carbon product, as set forth.

8. The process of continuously producing low-carbon metals or alloys,which consists in first producing a material relatively high in carbon,running the molten high-carbon product into a separate chamber andelectrically heating it in the presence of lime, and. separating theresulting calcium carbid from the low-carbon product, as set forth.

9. The process of continuously producing low-carbon metals or alloys,which consists in first producing a material relatively high in carbon,by electrically smelting a charge containing an excess of carbon,separating the resulting slag, running the molten highcarbon productinto a separate chamber and electrically heating it in the presence oflime, and separating the resulting calcium carbid from the low-carbonproduct, as set forth.

10. The process of continuously producing low-carbon metals or alloys,which consists in first producing a material relatively high in carbonby electrically smelting a charge containing an excess of carbon,separating the resulting slag, running the molten highcarbon productinto a separate chamber and electrically heating it in the presence oflime, separating the resulting calcium carbid from the low-carbonproduct, and supplying the charge mixture and lime and withdrawing theslag, calcium carbid and low-carbon product as required, as set forth.

1 1. The process of continuously producing low-carbon metals or alloys,which consists in first producing a material relatively high in carbonby electrically smelting, with carbon electrodes, a charge containing anexcess of carbon, protecting the electrodes from oxidation by aconsiderable body of the charge, separating the resulting slag, runningthe high-carbon product into a separate chamber having non-carbon wallsand treating it with lime, separating the resulting calcium. carbid fromthe low-carbon product, and supplying the charge mixture and lime andwithdrawing the slag, calcium carbid and low-carbon product as required,as set forth.

12. The process of producing low-carbon ferrochromium, which consists infirst producing ferrochromium relatively high in carbon, removing themolten highcarbon product from the zone of reduction and treating itwith a decarburizing agent, and separating the carburized reagent fromthe low-carbon product, as set forth.

13. The process of continuously producing low-carbon ferrochromium,which consists in first producing ferrochromium .relatively high incarbon, running the molten highcar bon product into a separate chamberand treating it with a decarburizing agent, and separating thecarburized reagent from the low-carbon product, as set forth.

14; The process of continuously roducing. low. carbon ferrochromium,"v;wh1c consists in first producing ferrochromiumrelativelyshigh'incarbon, runningthe molten high-car.- bonproduct into a separatechamber-and: electricallyheating it inthepresence of a de-; carburizing=.agent, and. separating the A carburized reagent from-the: low-carbon.product, as. set forth. r

15. The process of continuouslyf roducing lowcarbon ferrochromium, whicconsists. in first producing ferrochromiurn' relatively high incarbonby-electrically: smelting a charge containingan. excess of carbon,sepae. rating the resultingislag, running theimolten high-carbon productinto; a separate: chame-., her and electrically heatingiit in. thepresence of a decarburizing agent, and separating the. carburized reaent fromthe low-carbon. product, as set forth;

16. The process of continuously producinglow carbon ferrochromium, whichfCOIlSlStS infirst producing ferrochromium; relatively high in carbonrby electrically: .smelting,=a chargecontaining an excess of carbon,.sepa-.. rating the resulting slag, runningzthemolteni high-carbonproduct into; .a separate =cham... her and: electrically heating it in:the presence. of a decarburizing agent, separatingthecare burizedreagent fromthe low-carbon product,- and supplyinglthe chargernixtureland'decar.-.l burizingagent and withdrawing the slag,,carburized reagent and. low-carbon product as required, as set forth,

17. The process of continuously: roducing low carbon ferrochromium whichconsists in first producing-r-fer-rochromium;.relativel high in:carbonby electricallyl smelting, with carbon electrodes, .a .chargecontainlngtan-i, excess of carbon,::protecting theelectrodes fromoxidation.- by: a considerable body;- of

rateicha'mber having nonecarbon :walls and .treating it with adecarburizinigragent, sepa- 5 rating the carburized reagent om the low-.carbon product, and supplying the charge 1 zmixturesandadecarburizing aant and wit drawingtheslag, carburize reagent and low-carbon product asrequired, as set. fortlr. 5o

' 181 The-processof continuously roducing low carbon rferrochromium,wlncli consists 1 in firstproducing. ferrochromium relatively .highcarbon .by electrically smelting a charge containinglanexcess of carbon,sepa-. 5 5

- ratingthearesult-lng slag, running the highcarbonproduct into; aseparatechamber and treating .it with lime, separating the resulting.-calcium carbidl from the low-.carb on vpro duct,- and sup lyingthechargemixture and lime and I withdrawing. the 1 slag, calcium carbid and.low-carbon product as required, as set forth:

' 19.. The-process ofcontinuousl. roducing 10W carbon. :ferrochromium,which consists 6 5 in first producing ferrochromium relativel .high'incarbon. by; electrically? smelting, wit carbon-electrodes, a chargecontaining an excess of; carbon, .protecting the electrodesfromoxidationby a considerable body of the a charge, separating theresulting slag, running. thechigh-carbon:product into a separatechamber. having. non-carbon Walls 1 and treating it with lime,-separating the result- .ingscalciumtcarbid from the low-carbonproduct,.andnsupplying the charge mixture and -lime;andwithdrawing theslag, calcium carbid; and .low-carbonproduct as required, as-setwforthtIn: testimony whereof I affix my signature 0 in .presence of two.witnesses.

EDGAR F. PRICE.

the. 1 charge; separating; the resulting; slag, '-carbon' product into asepa-.

running. the big D. BURGESS.

